Marcial Boo, the head of Ipsa, said the 26 had been contacted at least four times to warn them they would be exposed. But in an angry response to being “named and shamed”, some MPs complained that Ipsa had not made them aware of the outstanding money until Thursday while two, including Dinenage, maintain they do not owe any money.

The amounts are small compared with the overall MPs expenses and offices budget – which rose by 1.6% to nearly £106m last year – but the smaller sums make it less worthwhile for Ipsa to pursue through complicated salary reductions or legal action.

MPs are issued with a credit card they can use for parliamentary business only, so a typical example of where they might owe money is if they have used the card for a political or personal purpose.

The naming and shaming, which has never been done before, ispart of Ipsa’s effort to get the money back but is also in the spirit of creating “more transparency which will lead to greater public trust”.

A spokesperson for David Cameron said: “The prime minister’s view is that any minister who owes money should pay it back.”

Dinenage, the minister for equalities, was accused by Ipsa of failing to repay £13.50 after using her MP’s payment card to settle a bill for her constituency office telephone.

She told the Guardian that the charge was mistakenly debited from the card by BT months ago and then credited back to the card the following month, and that she had no idea that Ipsa believed she owed money until today. “I have spent today being accused of being a thief instead of working for my constituency casework. It is a mistake on Ipsa’s part because I never owed the money in the first place.”

Spending on flats, hotels, travel and subsistence by MPs was down by about £150,000 at £11.6m, but staff costs and numbers have increased. MPs now employ more than 4,000 people, an increase of more than a third on six years ago.

Former Tory energy minister Charles Hendry, who stood down from parliament in May, was accused by Ipsa of spending £87.60 on a hotel in the London area, which cannot be claimed according to the rules.

Hendry has disputed the claim and has forwarded an email to the Guardian which appears to show that Ipsa told him in June this year that he had no outstanding debts. However, an Ispa spokesman claimed that Hendry was informed of this outstanding amount in March and April which was then written off.

Stephen Barclay, an assistant government whip, was named as owing £62 by the watchdog. He responded on Twitter by saying that he had not been contacted.

@SuttonIsle Not correct. Has now been repaid & was our inputting error re £62 but ipsa did not notify me and paid immediately once notified.

Laurence Robertson, the Tory MP for Tewkesbury, told the Gloucestershire Echo that Ipsa had “told lies” because the body had not contacted him over owing the same amount.

Tory backbencher Stewart Jackson, who was listed as owing a £7.50 parking charge, said he had been in “active discussions” with Ipsa but they nevertheless decided to write it off and publish, the Peterborough Telegraph reported.

He said he had forgotten to press the receipt button on the car park machine. “I think this list needs some scrutiny because I think you will find it is probably and not surprisingly errors on the part of Ipsa in processing legitimate claims,” he said.

Former Liberal Democrat MP Stephen Williams was listed as owing a £13.50 office telephone bill that fell outside the rules and a £195.68 overspend on his 2013-14 office costs budget.

Conservative MP David Mowat said the watchdog had admitted making a mistake by naming him. “The bill was in respect of a £35 invoice, to the information commissioner, which was correctly claimed,” he said. Ipsa responded: “Mowat has today provided additional information about his outstanding expenses and therefore the amount is no longer a written-off debt.”

Children’s minister Timpson selected “not claimed – to repay” when submitting a £127.70 expenses claim but has not yet returned the funds, Ipsa said. It said he had since contacted Ipsa to say he would repay the money.

A spokesman for Ipsa maintained that all MPs were notified of the debts on 20 July by email and letter and sent a follow-up email on 26 August. “It is the member’s job to submit the claim in a proper way,” he said.